It is known to store data representing a digital image in a image memory, and then to read out the data in a predetermined sequence, in order to generate a stream of pixel (picture element) data for controlling the display.
In such a system, it may be desired to "zoom" the image i.e. to expand or contract it by a specified magnification factor. This requires magnifying the image in both the X (horizontal) and Y (vertical) directions.
One object of the present invention is to provide an image display apparatus with such a zoom facility.
A particular problem arises when the display device is of the interlaced type i.e. displaying alternate frames with the raster lines of the two frames interlaced with each other. In this case, it is difficult to produce Y magnification by an odd factor, as well as by an even factor.
Another object of the present invention is therefore to overcome this problem.